Open Question
Epistatic gene interaction results in a modification of the F₂ dihybrid ratio.
Give two examples of modified F₂ ratios produced by epistatic gene interactions and describe how gene interaction results in the ratios.
3. Extensions to Mendelian Inheritance
Epistasis and Complementation
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How can you tell if two genes are epistatic?
A
The F2 offspring from a cross show a 9:3:3:1 phenotypic ratio
B
The F2 offspring all show a mutant phenotype
C
The F2 offspring show a phenotypic ratio that is NOT 9:3:3:1
D
The F2 offspring all show a wild-type phenotype
Verified step by step guidance1
Understand the concept of epistasis: Epistasis occurs when the effect of one gene is dependent on the presence of one or more 'modifier genes'. It can alter the expected phenotypic ratios in genetic crosses.
Recognize the typical Mendelian ratio: In a dihybrid cross, the expected phenotypic ratio for independent assortment is 9:3:3:1, which indicates no epistasis.
Identify deviations from the 9:3:3:1 ratio: If the F2 offspring show a phenotypic ratio that deviates from 9:3:3:1, it suggests that epistasis may be occurring.
Consider the phenotypes of the F2 offspring: If all F2 offspring show a mutant phenotype or all show a wild-type phenotype, this indicates a deviation from the expected ratio, suggesting epistasis.
Analyze the genetic interaction: Determine which gene is masking the effect of the other, leading to the observed phenotypic ratio. This will help confirm the presence of epistasis.
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Epistasis and Complementation practice set
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